THREE MUSKETEERS: Catcher John Buck, who hit one of the Mets’ three two-run home runs last night, celebrates at home plate with Lucas Duda in the fourth inning of the Mets’ 8-4 win over the Padres at Citi Field. Photo: Bill Kostroun

Matt Harvey wore sleeves only to the elbow on a 44-degree night at Citi Field, but he didn’t merely dress the part of tough guy. He was every bit Clint Eastwood last night, daring the Padres to make his day.

In the end, the Mets right-hander made manager Terry Collins’ day. Harvey’s 2013 debut was a beauty, giving the handful of fans in the ballpark a reason to celebrate the fact they showed up.

“It was one of those things I knew I was going to have to block out,” Harvey said, referring to the weather, after his one-hitter over seven shutout innings with 10 strikeouts led an 8-4 victory over the Padres. “It was cold for everybody.”

Lucas Duda, John Buck and Ike Davis all homered for the Mets, who have scored 19 runs in their first two games.

Everth Cabrera’s single leading off the fourth was the Padres’ only hit against Harvey, who closed his performance by retiring 10 of the final 11 batters he faced. Cabrera was picked off first base by Harvey, who didn’t allow a runner to reach second.

Harvey said a new pickoff move was among his offseason improvements.

“I attribute that to Ike, he kind of made fun of me for having a real bad pickoff move,” Harvey said. “So I definitely wanted to make it quicker and it’s something we worked on in spring training, and hopefully Ike won’t be saying that anymore.”

Harvey, who walked two, was finished after 94 pitches. The double-digit strikeout game was his third in 11 career starts. Harvey (1-0) received his first career Citi Field victory after going 0-2 with a 1.88 ERA in four starts here last season.

“He’s a little different than he was last fall,” Collins said. “Last fall he wanted to show everybody his stuff was plus stuff, which we had all heard, but he’s becoming a pitcher.”

Buck said he knew right from the start it could be a special game for Harvey, who struck out four in the first two innings.

“Overall his stuff is electric,” Buck said. “He was getting a lot of swings and misses late in counts with that elevated fastball.”

Harvey even contributed a second-inning single, but refused to wear the customary warmup jacket for pitchers on the bases.

“I like to play baseball, and in my mind a jacket doesn’t belong on a baseball field,” Harvey said.

The Mets seized control with four runs in the fifth inning to take a 8-0 lead. Davis’ two-run homer against Clayton Richard (0-1) was the big hit in the inning. Davis rebounded from an 0-for-5 in the opener that included four strikeouts.

Collin Cowgill had reached on a throwing error by third baseman Jedd Gyorko to begin the inning. David Wright’s RBI double made it 5-0, before Davis unloaded. Buck delivered an RBI single for the Mets’ final run of the inning.

The Mets built a 4-0 lead in the fourth on Buck’s two-run homer against Richard. Duda doubled before Buck hit a line drive to right field that kept carrying until it cleared the fence.

Duda got the Mets started with a monstrous home run in the second. After Marlon Byrd singled leading off, Duda crushed a 1-1 fastball from Richard to the porch in right field. Maybe the best sign for the Mets was the blast came against a left-handed pitcher. Last season, Duda had only four homers in 134 at-bats against lefties.

“Both Duda and Ike [homering] off a lefty is huge,” Collins said. “If those two guys are swinging the bat like they can, hitting balls in the seats, it’s going to be a tough lineup to get through, because there are no breaks.”